Clinical Scorecard: Analysis of Tumor Control and Toxicity in Benign Intracranial Tumors Treated with HyperArc Radiosurgery Using a Frameless Linac System
At a Glance
Category
Detail
Condition
Benign intracranial tumors
Key Mechanisms
Automated single-isocenter volumetric modulated arc therapy (VMAT) radiosurgery using HyperArc™ with flattening filter-free beams and high dose rates to deliver conformal high-dose radiation sparing normal brain tissue
Target Population
Patients with benign intracranial tumors eligible for radiosurgery, excluding Grade III meningiomas, including those with prior surgery or radiation
Care Setting
Radiation oncology departments using frameless linac-based radiosurgery systems with HyperArc™ technology
Key Highlights
HyperArc™ enables automated, efficient, and high-quality radiosurgery plans using multiple arcs and 10 MV flattening filter-free beams with high dose rates.
Treatment planning involves precise target delineation using CT and MRI fusion without additional PTV margin, normal tissue sparing, and rigorous quality assurance including radiochromic film or diode array verification.
Intrafraction motion is minimized and monitored using optical surface imaging and 6 degrees of freedom couch corrections, achieving submillimeter accuracy.
Guideline-Based Recommendations
Diagnosis
Use high-resolution CT simulation with 1 mm slice thickness from above cranium to C2 vertebrae.
Register thin-sliced (1 mm) T1-weighted post-contrast MRI to CT for accurate tumor delineation unless contraindicated.
Exclude Grade III meningiomas from radiosurgery candidacy.
Management
Deliver radiosurgery using HyperArc™ automated VMAT plans with 2-4 arcs at fixed angles on a Varian Edge linac with 10 MV flattening filter-free beams.
Normalize prescription dose to cover ≥ 99% of gross tumor volume (GTV) without additional planning target volume (PTV) margin.
Adjust fractionation and dose based on tumor type and size.
Perform pre-treatment patient-specific quality assurance using radiochromic film or 2D diode array to verify dose accuracy and geometric alignment.
Monitoring & Follow-up
Use orthogonal kV imaging and cone beam CT for patient positioning with 6 degrees of freedom corrections prior to treatment.
Continuously monitor intrafraction motion with optical surface imaging to maintain submillimeter accuracy.
Follow patients with brain imaging at least 3 months post-treatment to assess tumor control and toxicity.
Risks
Potential toxicity to critical structures if tumor is within 1.5 mm and receives high dose (≥8 Gy near brainstem or ≥3 Gy near optic structures/cochlea).
Risk minimized by precise planning, dose conformity, and gradient indices.
Patient & Prescribing Data
Patients with benign intracranial tumors treated between May 2018 and October 2021 with at least 3 months follow-up imaging
HyperArc™ radiosurgery achieves high conformity and steep dose gradients with minimal toxicity, enabling effective tumor control without additional PTV margins.
Clinical Best Practices
Use frameless immobilization with Encompass™ open mask for patient comfort and reproducibility.
Collaborate with neurosurgeons and radiation oncologists for accurate target contouring.
Perform rigorous quality assurance including machine QA per AAPM TG-142 guidelines and patient-specific QA before treatment.
Employ continuous intrafraction motion monitoring and 6 degrees of freedom couch corrections to ensure treatment accuracy.
Customize fractionation and dose based on tumor characteristics and proximity to critical structures.
by Whitney S. Hotsinpiller, Evan M. Thomas, Ian Tsekouras, Richard A. Popple, Markus Bredel, Christopher D. Willey, Barton L. Guthrie, James M. Markert, Kristen O. Riley, John B. Fiveash, Drexell Hunter Boggs
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